In recent years, light emitting diodes (LEDs) have emerged as efficient, inexpensive, long-lasting light sources that produce little heat and require little maintenance. LEDs have been quickly adopted for applications that use colored light, such as red, yellow and green traffic lights, and are making inroads for illumination applications that use generally white light.
A good application for white-light LEDs is overhead street lighting, where LEDs mounted in downward-facing fixtures at the top of a series of poles illuminate the street below. The light output from LEDs is fairly directional, so that if bare LEDs were mounted in the fixtures and pointed downward, the bottom of the light poles would be significantly brighter than the street area between the poles.
Accordingly, there exists a need for an optic, preferably a lens, which can redistribute the light output from each LED, so that light from a series of the overhead-mounted LEDs and optics produces a more uniform illuminance at the street level. Such an optic may be used in other applications that require generally uniform illuminance at an observation plane from a series of discrete point-like sources laterally spaced away from the observation plane.